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what is measles:-

MEASLES
Microbiology
what is measles:-
Measles is a single-stranded RNA paramyxovirus with one
antigenic type. Humans are the only reservoir. Measles
virus infects the upper respiratory tract and regional lymph
nodes and is spread systemically during a brief, low-titer
primary viremia. It is more prevalent in winter and spring.
A secondary viremia occurs within 5–7 days when virus infected
monocytes spread the virus to the respiratory tract,
skin, and other organs. The characteristic histological  finding
is the presence of large, multinucleated giant cells (Warthin-
Finkeldey cells) and syncytium formation in respiratory
epithelia and reticulo-endothelial cells. Virus is present
in respiratory secretions, blood, and urine of infected
individuals. Measles virus is transmitted by large droplets
from the upper respiratory tract and requires close contact.
Incubation Period
Eight to twelve days from exposure to the onset of symptoms
Infective Period
Period of infectivity is from 1 to 2 days before symptoms (about
5 days before onset of rash) to 4 days after the appearance of
the rash.
Mode of Transmission
Measles is highly contagious. Measles virus is typically
transmitted by respiratory droplets, direct contact, or vomits
Infants less than one year rarely acquire measles due to passage
of maternal antibodies.
Clinical Features
*Stages of Infection
Classic measles infection can be subdivided into the following
clinical stages: prodromal, eruptive, and convalescent.
1-Prodromal: The prodromal  usually lasts for 2–3 days but may
persist for as long as 8 days
The prodromal  phase is defined by the appearance of
symptoms which typically include fever, malaise, and anorexia,
followed by conjunctivitis, coryza, and cough. The severity of
conjunctivitis is variable and may also be accompanied by
lacrimation or photophobia. The respiratory symptoms are due
to mucosal inflammation from viral infection of epithelial cells.
Fever is typically present; the pattern may be variable. Various
fever patterns have been described; fever as high as 40oC can
occur.
Koplik’s spot: Patients may develop an enanthem known as
Koplik’s spots; Koplik’s spots (Fig. 2) in patients with suspected
measles, are considered pathognomonic for measles infection
and occur approximately 48 hours before the characteristic exanthem appears.These are 1 to 3 mm whitish, grayish,
or bluish elevations with an erythematous base, typically seen
on the buccal mucosa opposite the molar teeth, though they
can spread to cover the buccal and labial mucosa as well as the
hard and soft palate. They have also been described as “grains
of salt on a red background”. Koplik’s spots subsequently may
coalesce and generally last 12 to 72 hours.
2-Eruptive phase: Starts on 4–5th day of illness when fever
rises again. The exanthem of measles is a maculopapular
, blanching rash beginning on the face and spreading
cephalocaudally and centrifugally to involve the neck, upper
trunk, lower trunk, and extremities. The lesions may become
confl uent, especially in areas such as the face, where the rash
develops first. The rash may also have some petechiae; in severe
cases, it may appear hemorrhagic. In general, the extent and
degree of confluence of the rash correlates with the severity of
the illness in children. The palms and soles are rarely involved.
The cranial to caudal progression of the rash is characteristic
of measles but is not pathognomonic.
Other characteristic findings during the exanthematous
phase include lymphadenopathy, high fever (peaking two to
three days after appearance of rash), pronounced respiratory
signs including pharyngitis, and nonpurulent conjunctivitis.
Koplik’s spots often begin to slough when the exanthem
appears.
Clinical improvement typically ensues within 48 hours of
the appearance of the rash. After three to four days, the rash
darkens to a brownish color and begins to fade, followed by
fine desquamation. The rash usually lasts six to seven days.
Hyperpigmented skin lesion may persist long after active
measles infection, and is an evidence of post-measles infection.
Hyperpigmented skin lesion may persist long after active measles infection and an evidence of post-measles infection
3-Convalescent phase: Cough may persist for one to two weeks
after measles infection. The occurrence of fever beyond the
third to fourth day of rash suggests a measles-associated
complication. Immunity after measles infection is thought to be
lifelong, although there are rare reports of measles re-infection.
Diagnosis
Mostly clinical depending upon history and clinical examination.
Koplik’s spot seen is pathognomonic. Post-measles desquamation
and hyperpigmentation are too characteristics. Cases of modified
measles and atypical measles could be confusing when measles
specifi c antibody in paired sera is useful.
Differential Diagnosis
• Other exanthematous immune-mediated illnesses and
infections,
– Rubella (rash is similar but prodrome is milder,
there is a prominent retroauricular or suboccipital
lymphadenopathy)
– Adenoviruses
– Enteroviruses
– Epstein-Barr virus (characterized by sore throat,
lymphadenopathy and splenomegaly)
• Exanthem subitum or Roseola infantum rash usually
appears after disappearance of fever and erythema
infectiosum (in older children)
• Mycoplasma pneumoniae and group A Streptococcus may
also produce rashes similar to measles
• Kawasaki syndrome: It can manifest many of the same
findings as measles but lacks discrete intraoral lesions
(Koplik’s spots) and a severe prodromal cough. Typically
has elevated neutrophils and acute-phase reactant levels.
In addition, the characteristic thrombocytosis of Kawasaki
syndrome is absent in measles
• Drug eruptions (history of specific drug consumption).
Laboratory Investigations
• Complete blood count (CBC)
Leukopenia, T-cell cytopenia, and thrombocytopenia may
be observed during measles infection
• Chest radiography may demonstrate interstitial
pneumonitis
• Biopsy samples of lymphoid tissues before the appearance
of the exanthem may demonstrate reticuloendothelial
giant cells.
• Histologic analysis of  enanthem or exanthem and cytologic
examination of nasal secretions may also demonstrate
epithelial giant cells.
Treatment
Mainly symptomatic and supportive with nutritional support
• Maintenance of hydration, oxygenation, and comfort are
goals of therapy
• Antipyretics for comfort and fever control
• For patients with respiratory tract involvement, airway
humidification and supplemental oxygen
• Ventilatory support may be required for respiratory failure
due to croup or pneumonia
• Antiviral therapy is not effective in otherwise normal
healthy patients
• Antibiotics are indicated in superadded bacterial infection
in the convalescent phase.
Vitamin A in Measles
Vitamin A can reduce the severity and complications of
measles. Published studies revealed that measles associated
death increases about 24% in vitamin A deficient children.
Dose of Vitamin A
200,000 1U orally for children ≥1 year of age and 100,000 IU for
children 6 months to 1 year of age, two doses on D1 and D2.
Patients suffering from measles should be off ered protein
and energy-dense diet and increment of two additional daily
diets at least for 6 weeks to prevent subsequent malnutrition.
Complications
Case fatality from complications of measles, in developing
countries is 4–6%. Risk groups for developing complications are:
• Immuno-compromised hosts
• Pregnant women
• Individuals with vitamin A deficiency or poor nutritional
status
• Individuals at the extremes of age.
Measles causes disseminated infection, so multiple systems
and organs are affected.
• Pulmonary: Respiratory tract infections (most frequently
occurs among patients <5 years and >20 years)
– Interstitial pneumonia
– Post-measles bronchopneumonia due to Streptococcus
pneumoniae, Streptococcus pyogenes, Haemophilus
infl uenzae, and Staphylococcus aureus
– Laryngotracheobronchitis (croup both pre-eruptive
croup and posteruptive croup)
– Otitis media occurs in 5 to 10 percent of cases
– Bronchiectasis
– Flaring up of latent tuberculosis
– Coinfection with other viruses like parainfl uenza and
adenovirus.
• Neurologic
– Febrile seizure
– Encephalitis: Usually appears within a few days of
the rash. It is associated with a CSF pleocytosis (predominantly
lymphocytes), increased protein levels,
and normal glucose
– Acute disseminated encephalomyelitis: Acute
disseminated encephalomyelitis (ADEM) is a demyelinating
disease that presents during the recovery phase
of measles infection, typically within two weeks of the
exanthem. ADEM is also known as postinfectious or
postvaccination encephalomyelitis
– The major manifestations of ADEM include fever,
headache, neck stiff ness, seizures, and mental status
changes such as confusion, somnolence, or coma.
Other findings may include ataxia, myoclonus,
choreoathetosis, and signs of myelitis, such as
paraplegia, quadriplegia, sensory loss, loss of bladder
and bowel control, and, in patients with myelitis,
back pain. Analysis of cerebrospinal fl uid generally
demonstrates a lymphocytic pleocytosis and elevated
protein concentration
– Subacute sclerosing panencephalitis
– Subacute sclerosing panencephalitis (SSPE) is a fatal,
progressive degenerative disease of the central nervous
system that occurs 7 to 10 years after natural measles
infection
– Others
Other neurologic complications associated with measles
include acute measles-induced encephalopathy
• Malnutrition
Measles is a common antecedent of malnutrition (Fig.
4), lasting for 2–4 weeks in healthy children and it can
also increase the severity of malnutrition and can make
previously existing nonsevere malnutrition to severe acute
malnutrition (SAM), a potentially serious condition with
high-case fatality.
• Eye manifestations
– Measles-induced keratitis (a common cause of
blindness)
– Corneal ulceration
• Gastrointestinal
– Gingivostomatitis
– Diarrhea
– Gastroenteritis
– Hepatitis
– Mesenteric lymphadenitis
– Appendicitis.
In developing countries, measles-induced stomatitis and
diarrhea can lead to worsening of nutritional status.
• Cardiac
Cardiac complications of measles include myocarditis and
pericarditis
• Immunosuppression: Measles infection can lead to
systemic immune suppression and severe secondary
infections, especially in the developing world. These
eff ects are caused by direct infection of T cells by measles
virus and by infection of dendritic cells, impairing their
important antigen presenting/accessory function in T cell
activation.
Due to immunosuppressant properties, children
suffering from bronchial asthma may get temporary
relief of breathing difficulty as it behaves like steroid.
However its adverse effects in such cases far outweigh its
bronchodilator property. Similarly, children with nephritic syndrome with measles may develop brisk diuresis as it also
works here as steroid (immunosuppressant).
Prevention
• Isolate the patient during its infective period
• Measles vaccine given within 72 hours of exposure can
prevent measles in contact as incubation period of vaccine
measles virus is less than natural measles virus and
produces immunity earlier than natural measles virus, due
to earlier subclinical infection of attenuated vaccine virus.
Measles Vaccine
With the absence of an intermediary host, measles vaccine
has generated a lot of interest for potential eradication. Hence
the measles vaccination has a lot of importance at the national
and international level. Maternal antibody provides protection
for first 6 to 9 months of infancy. A number of live attenuated
vaccines are available against measles either as monovalent
measles vaccine or measles containing vaccine (MCV). The
MCV are MMR (measles, mumps and rubella), MMRV (measles,
mumps, rubella, and varicella) and MR (measles and rubella).
Two doses of measles vaccine are given. Th e fi rst dose is
given with MR (measles and rubella) in EPI schedule. The
second dose is given at 15th month as monovalent measles
vaccine according to EPI schedule. However instead of
monovalent measles vaccine given by EPI, measles vaccine
containing combination vaccine MMR (measles, mumps, and
rubella) can be given at 15th month.
In areas with high measles transmission, the first dose of
MCV (MR, MMR) should be administered at nine month. All
unvaccinated children over nine month should receive their
vaccine as soon as possible. In countries with low risk of measles
transmission, the first dose may be administered at 12 months.
The optimum timing for second dose is 15 to 18 months.
Measles vaccines are safe, effective, inexpensive and
provide long lasting immunity. Hence all countries should aim
at providing two doses of vaccine.


what is measles:-

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